1. Field of the Invention
This invention relates to optical endoscopes and imaging systems.
2. Discussion of the Related Art
Contemporary medical technology uses x-rays, sound waves, and visible light to produce in vivo images of biological tissues. Visible light and infrared (IR) imaging has better potential resolution than is obtainable with sound waves, because visible light and IR light have shorter wavelengths than sound waves. In spite of this advantage, some in vivo imaging systems use sound waves, because visible and IR light does not penetrate thick tissues. Consequently, many in vivo imaging systems do not have the image resolution obtainable in systems based on visible or IR light.
One method that enables using visible and IR light in medical imaging entails the use of endoscopes that are inserted into the body being imaged. Present medical technology uses endoscopes in both non-invasive and invasive techniques. In the non-invasive techniques, the endoscope is inserted into hollow body structures such as arteries, veins, and the digestive tract. In the invasive technique, the endoscope is inserted into interiors of solid body tissues. Unlike the non-invasive techniques, invasive endoscopy typically produces some tissue damage during insertion of the endoscope. The tissue damage is particularly undesirable in sensitive organs such as the brain. Such tissue damage has limited the use of invasive endoscopy and of optical techniques for imaging interiors of solid tissues.
Various embodiments provide optical micro-probes for use in imaging and monitoring. The optical micro-probes can have smaller diameters than conventional endoscopes. Exemplary optical micro-probes have diameters of 0.127 millimeters (mm) as compared to a typical endoscope diameter of about 0.5 mm to 4 mm. The smaller diameters enable inserting the new optical micro-probes into body tissues via narrow needles, e.g., 31 gauge needles, which reduces tissue damage during invasive endoscopy.
One embodiment according to principles of the invention features an optical system for monitoring or imaging a sample. The system includes an optical micro-probe, an optical splitter or circulator, and an optical detector. The optical micro-probe includes an optical fiber and a graded refractive index (GRIN) fiber-size lens fused to one end of the fiber. The optical splitter or circulator receives light from a source and directs a portion of the received light to the optical fiber. The optical detector is coupled to receive a portion of light collected from the sample by the GRIN fiber-size lens and is configured determine a characteristic of the sample from the received light.